1. Field of the Invention
The present invention relates to a therapeutic device for treating a tissue of a living body, by holding, coagulating and cutting the tissue.
2. Description of the Related Art
Conventionally-known living tissue therapeutic devices generally include a pair of holding members for holding a tissue of a living body, in which a heat generator is provided on one or both sides of the holding members and the heat generator is turned on to generate heat while holding a tissue so as to coagulate the tissue or cut the coagulated portion. The tissue treatment devices of this type are used for various cases, such as hemostasis of a blood vessel contained in a living tissue, cauterization of a diseased portion or bleeding point on a surface layer of a living tissue, and blockage of the oviduct for the purpose of contraception. A living tissue therapeutic device is used to stop bleeding from a blood vessel or block the oviduct, and can coagulate a tissue of a living body of the patient that needs to be treated. Further, the coagulated living tissue can be cut with the therapeutic device.
For example, U.S. Pat. No. 5,792,137 discloses a treatment device including a silicon semiconductor serving as a heat generator having a sharp female cutting edge at the holding section of the holding forceps, and with this device, electricity is applied to the silicon semiconductor to generate heat due to its resistance, so as to coagulate the tissue of a living body and cut it.
U.S. Pat. No. 4,219,025 and U.S. Pat. No. 4,231,371 each disclose a technique in which a plurality of heater elements are provided on a cutting blade made of an electrical insulating material, and these heater elements are constructed separate from each other so that they can be controlled independently, thus making it possible to keep the temperature of the cutting edge constant.
U.S. Pat. No. 5,593,406 discloses a treatment device including a hook-shaped resistance heating portion provided at the distal end portion of the insertion section, and with this device, a tissue from a living body is cut while heating it.
U.S. Pat. No. 5,308,311 discloses a treatment device including a sharp female cutting blade provided at the distal end portion, and a heating element provided on a side surface of the female cutting blade, and with this device, a tissue from a living body is cut while coagulating it with the side surface.
Jpn. Pat. Appln. KOKAI Publication No. 6-7366 and German Utility Model Application G8809437 each disclose holder forceps provided with an adjustable stopper mechanism at the handle portion; however they are not of a type equipped with a heat generator at the holder portion for holding a living tissue for coagulating and cutting the tissue.
However, with the technique disclosed in U.S. Pat. No. 5,792,137, described above, an uneven distribution of temperature results because it contains only one heat generator. More specifically, usually, heat generators which generate heat by way of electrical resistance have positive temperature coefficients. In other words, when the temperature increases, the electrical resistance increases, whereas when the temperature decreases, the electrical resistance decreases. With this structure, if a living tissue is held by a part of the heat generating portion, the temperature of the portion which is in contact with the tissue decreases, and therefore the electric resistance partially decreases. The calorific value is determined by R×I×I (R is resistance and I is current), and therefore the calorific value of the portion in contact with the living tissue decreases, and the temperature of that portion decreases. Here, even if the output is increased attempting to compensate for this, the temperature of the portion in contact with the living tissue will not increase, but only the other portion, which is not in contact with the tissue, heats up. As a result, an uneven distribution of temperature is created, and therefore it requires much time to coagulate and cut the tissue.
Further, the heat generator is bonded to the holder portion in its entire surface, and therefore, with this bonding method, a large contact surface is involved. As a result, there is a drawback of heat being radiated as it is propagated to the holder portion. Further, since the contact surface is made of a metal and therefore is hard, if there is even a slight gap between holding pieces when they are closed, the tissue cannot be accurately treated (especially it cannot be properly cut).
Further, U.S. Pat. No. 4,219,025 and U.S. Pat. No. 4,231,371 are directed to a structure in which the cutting edge is on one side, and hemostasis and coagulation are carried out by lightly pressing the device onto a living tissue; therefore such a technique of treating a living tissue while holding it is not considered in these documents. This structure also entails the problem of the coagulation force being weak.
Furthermore, U.S. Pat. No. 5,308,311 is also directed to a structure in which the cutting edge is on one side, and hemostasis and coagulation are carried out by lightly pressing the device to a living tissue; therefore such a technique of treating a living tissue while holding it is not considered in this document. This structure also entails the problem of requiring much time to coagulate a living tissue.